Silent video is boring to watch. Even if it's something interesting. If you put the exciting sligshot around the moon footage from the movie "Armageddon" and turn the sound off so it is silent (like it would be in space), very few people will watch it without reaching for the volume control.
Boring video can be made entertaining with a decent soundtrack. Wedding videos that people sit and watch all the way through in one sitting are the perfect example. Put an enjoyable, identifiable song on and most people will watch anything.
Sonicfire Pro 4.